Garden Q&A: Deadhead annuals, perennials for more blooms

Saturday

Jul 28, 2007 at 12:01 AMJul 28, 2007 at 8:10 AM

QUESTION: Now that the blooms on some of my annuals and perennials have faded, the plants are looking a bit ratty. I’ve heard of people picking off the dead flowers. Can this be done for all annuals and perennials? What is the best way to go about this? — M.N., Rockford

ANSWER: Failure to deadhead can cause a plant to appear leggy — that is, having stems that are too long, with not enough blooms or leaves. Deadheading will help your plants look more full and bushy, as well as promote healthier plants and keep your gardens and container plantings looking neat and tidy.

The general procedure is to remove the plant’s dead flowers and, where applicable, the developing seedpod (when the seedpod is located behind the flower, rather than in the center of it). Some flowers can be removed simply by pinching them off with your fingers. If the stem is too tough, you should use bypass pruners. These have a sharp blade that slides over the bottom blade, providing a clean cut that does not damage the plant. Do not use an anvil pruner, as the movement of the blade onto the anvil will crush the stem.

Deadheading annuals that have been planted in containers is especially important, as their ability to bloom is already limited by constricted root growth and hotter soil conditions. Some annuals that respond well to pinching include snapdragons, cosmos, marigolds, petunias, geraniums and zinnias. However, some plants, such as impatiens, will naturally drop their blooms and don’t need deadheading.

For perennials, you should use a bypass pruner. Generally, you’ll want to cut above the first full set of leaves. Be sure to remove only the dead flowers from the plant. If you’re not careful, you could accidentally remove new buds that are about to turn into flowers.

For daylilies, you can either pinch off the dead flower each day or wait for all the blooms on the scape (stem) to die and remove the entire stem. There are other perennials that need to be deadheaded all the way to the ground or basal foliage (the set of leaves closest to the ground), such as coral bells and lady’s mantle.

However, there are some perennials that should not be deadheaded. For example, hydrangea and false indigo (a native plant) produce attractive seed heads.

Other perennials should not be deadheaded to encourage self-seeding (dropping seed that will germinate in areas around the plant), including columbine, yarrow, purple coneflower, bishop’s weed, bugleweed and dame’s rocket.

Finally, some plants are not deadheaded or cut back because they help to attract wildlife and birds, such as joe-pye weed, sunflower, gay feather, bee balm, black-eyed Susan and hosta.

It might be helpful to use a bucket to collect the dead flowers you remove, as they would make an excellent addition to a compost pile.

"Deadheading" is the term for removing the spent blooms on your plants. This not only improves the look of the plant, but also prevents the plant from going to seed and lets the plant put its energy into producing more flowers. Once a plant starts to produce seed, flowering declines. It is often desired to direct the plant’s energy away from making seeds and towards promoting more vegetation and stronger roots.

Master Gardeners can be contacted weekdays at the University of Illinois Extension office at 815-986-4357 and Monday and Tuesday from 9 a.m. to noon at Klehm Arboretum, 815-965-8146. You can also bring your questions to the plant clinic on Thursday evenings from 6 to 8 p.m. at Sinnissippi gardens just south of the greenhouse.